Epiphany

The time of appearance, meaning the period when the star
appeared to the wise men of the East. The 6th January is the Feast of
the Epiphany

The word is not special to Christianity. One of the names of Zeus
was Epiphanes (the manifest one), and festivals in his honour were
called “Epiphanies.” (Greek, epi-phaino, to shine upon, to be
manifest [in creation].)